In commercial fishing operations, the method of fishing known as purse seine fishing is an effective and widely used technique. The method is conceptually simple. A seine, or net, is fitted at one end with buoyant devices (e.g. floats) and is fitted at the other end with weighting devices (e.g. sinkers). As the seine is deployed in a rough circle, the weighted end of the seine submerges to cause the seine to hang essentially vertically in the water. To provide for seine retrieval, a purse line is attached to the weighted end of the seine by a plurality of connectors, known as purse rings. As the purse line is tightened by fishermen on the fishing vessel, the weighted end of the seine is drawn together to enclose fish within the seine. The weighted end, now pursed, is raised and drawn toward the fishing vessel. Simultaneously, support craft retrieve and draw in the buoyed end of the seine. In this way, fish are trapped in the seine as it is retrieved.
During seine retrieval, the purse line, through its interaction with the purse rings, is used to both purse the seine and draw it toward the fishing vessel. As can be easily imagined, the forces which are generated between the purse line and the purse ring during these operations can be very substantial. Indeed, these forces can create significant strain on components within the purse ring and lead to deformation and, eventually, a complete failure of the purse rings and a fraying of the purse line which causes the purse line to snag on the netting. In either event, the operation is compromised and the purse rings may need to be replaced.
Recent developments in the commercial fishing area have compounded the problem of purse ring wear because many of the now preferred fishing grounds are located in the Western Pacific Ocean. It happens, however, that purse seiner operations in the Western Pacific require deeper deployment of the seines than in other Pacific areas, because thermoclines in the Western Pacific often result in deeper schooling of food fish. Consequently, with the deployment of seines, the forces required to retrieve the seines (e.g. forces between the purse line and the purse rings) are greatly increased for longer periods of time. As a further consequence, standard purse rings, such as are used in other oceans of the world, are generally inadequate for use in the Western Pacific.
In light of the foregoing, the present invention recognizes the need to significantly increase the durability of purse ring components against significant strain forces, to permit efficient seiner operations at greater depths in the ocean, and to prolong the useful life of purse rings used in seiner operations regardless of depth. It is therefore an object of the present invention to provide a method of manufacturing purse rings for use in purse seiner fishing operations which has a relatively long period of usefulness. It is a further object of the present invention to provide a method for manufacturing purse rings for seiner operations that reduce tolerances between moveable components in the purse ring. It is yet a further object of the present invention to provide a method for manufacturing purse rings for use in purse seiner operations that utilize heat-treated and hardened steel components. Another object of the present invention is to provide a method for manufacturing purse rings for purse seiner fishing operations which is relatively easy perform, which is comparatively cost-effective, and which results in purse rings having improved strength.